Major Advance in Artificial Photosynthesis
Major Advance in Artificial Photosynthesis Poses Win/Win for the Environment
-Berkeley Lab Researchers Perform Solar-powered Green Chemistry with Captured CO2
Σημαντική
πρόοδος για το πεδίο της τεχνητής φωτοσύνθεσης, καθιστά την μέθοδο
διπλά επικερδή για το περιβάλλον, με την χρήση απομονωμένου διοξειδίου
του άνθρακα από την »πράσινη» χημεία, συμπεριλαμβανομένης της παραγωγής
καυσίμων από ανανεώσιμες πηγές. (Photo by Caitlin Givens)
H ανάπτυξη συστήματος το οποίο μπορεί να εγκλωβίσει τις εκπομπές διοξειδίου του άνθρακα πριν εξαερωθεί στην ατμόσφαιρα και στη συνέχεια, τροφοδοτούμενο από ηλιακή ενέργεια, να το μετατρέψει σε χρήσιμα χημικά παράγωγα, μεταξύ άλλων, βιοδιασπώμενα πλαστικά, φαρμακευτικά σκευάσματα, αλλά και υγρά καύσιμα, συνιστά δυνητικά επαναστατικό επίτευγμα, όσον αφορά στο πεδίο της τεχνητής φωτοσύνθεσης.
Οι επιστήμονες στο Lawrence Berkeley National Laboratory
(Berkeley Lab) του Υπουργείου Ενέργειας των ΗΠΑ (DOE) και το Πανεπιστήμιο της Καλιφόρνια (UC) Berkeley, έχουν δημιουργήσει ένα υβριδικό σύστημα νανοσυρμάτινων ημιαγωγών και βακτηρίων, το οποίο μιμείται τη φυσική φωτοσυνθετική διαδικασία με την οποία τα φυτά απορροφώντας ηλιακό φώς, συνθέτουν υδατάνθρακες από διοξείδιο του άνθρακα και νερό. Ωστόσο, το νέο σύστημα τεχνητής φωτοσύνθεσης, συνθέτει συνδυασμό διοξειδίου του άνθρακα και νερού σε ακετοξικά ανιόντα, τα πιο κοινά δομικά στοιχεία για τη βιοσύνθεση στις ημέρες μας.
Όσο περισσότερο διοξείδιο του άνθρακα απελευθερώνεται στην ατμόσφαιρα, τόσο η θερμοκρασία της αυξάνεται. Το ατμοσφαιρικό διοξείδιο του άνθρακα βρίσκεται σήμερα στο υψηλότερο επίπεδο των, τουλάχιστον, τριών εκατομμυρίων χρόνων, ως βασικό επακόλουθο της καύσης ορυκτών καυσίμων. Ωστόσο, αυτά και κυρίως ο άνθρακας, δεν θα πάψουν στο εγγύς μέλλον, να συνιστούν σημαντική πηγή ενέργειας για την κάλυψη ανθρωπίνων αναγκών και παρά την επιδίωξη χρήσης τεχνολογιών, οι οποίες απομονώνουν τον άνθρακα πριν διαφύγει στην ατμόσφαιρα, οι απαιτήσεις φύλαξής του, συνιστούν περαιτέρω περιβαλλοντική πρόκληση.
Η μέθοδος της τεχνητής φωτοσύνθεσης που αναπτύχθηκε από τους ερευνητές του Berkeley, λύνει το πρόβλημα αποθήκευσης με την ορθή χρήση του δεσμευμένου διοξειδίου του άνθρακα.
»Στη φωτοσύνθεση που διενεργείται από την φύση, την ηλιακή ενέργεια συλλέγουν τα φύλλα και το διοξείδιο του άνθρακα μειώνεται, καθώς συνδυαζόμενος με νερό, συνθέτει μοριακά προϊόντα που σχηματίζουν τη βιομάζα», λέει ο Chris Chang, ειδικός σε καταλύτες ενεργειακών μετατροπών με ουδέτερο ισοζύγιο άνθρακα. «Στο σύστημα μας, την ηλιακή ενέργεια συλλέγουν νανοσύρματα, τα οποία παραδίδουν ηλεκτρόνια σε βακτήρια, το διοξείδιο του άνθρακα συνδυάζεται με νερό και στην συνέχεια συνθέτει ποικιλία στοχοθετημένων χημικών προϊόντων προστιθέμενης αξίας.«
Συνδυάζοντας βιοσυμβατές φωτοευαίσθητες νανοσυρμάτινες συστοιχίες με επιλε-γμένους πληθυσμούς βακτηριδίων, το νέο σύστημα τεχνητής φωτοσύνθεσης καθίσταται διπλά επωφελές για το περιβάλλον, αφενός με την ηλιακά τροφο-δοτούμενη »πράσινη» χημεία και αφετέρου με την χρήση απομονωμένου διοξειδίου του άνθρακα.
Read via Berkeley Lab
A potentially game-changing breakthrough
in artificial photosynthesis has been achieved with the development of a
system that can capture carbon dioxide emissions before they are vented
into the atmosphere and then, powered by solar energy, convert that
carbon dioxide into valuable chemical products, including biodegradable
plastics, pharmaceutical drugs and even liquid fuels.
Scientists with the U.S. Department of
Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and
the University of California (UC) Berkeley have created a hybrid system
of semiconducting nanowires and bacteria that mimics the natural
photosynthetic process by which plants use the energy in sunlight to
synthesize carbohydrates from carbon dioxide and water. However, this
new artificial photosynthetic system synthesizes the combination of
carbon dioxide and water into acetate, the most common building block
today for biosynthesis.
“We believe our system is a revolutionary
leap forward in the field of artificial photosynthesis,” says Peidong
Yang, a chemist with Berkeley Lab’s Materials Sciences Division and one
of the leaders of this study. “Our system has the potential to
fundamentally change the chemical and oil industry in that we can
produce chemicals and fuels in a totally renewable way, rather than
extracting them from deep below the ground.”
Οι
τέσσερις συνιστώσες του καινοτόμου συστήματος τεχνητής φωτοσύνθεσης (1)
συλλογή ηλιακής ενέργειας, (2) παραγωγή μειωμένων ισοδυνάμων, (3)
αναγωγή του διοξειδίου του άνθρακα σε βιοσυνθετικά ενδιάμεσα και (4)
παραγωγή χρήσιμων χημικών. (credits ACS Publications)
Yang, who also holds appointments with UC
Berkeley and the Kavli Energy NanoSciences Institute (Kavli-ENSI) at
Berkeley, is one of three corresponding authors of a paper describing
this research in the journal Nano Letters. The paper is titled “Nanowire-bacteria hybrids for unassisted solar carbon dioxide fixation to value-added chemicals.”
The other corresponding authors and leaders of this research are
chemists Christopher Chang and Michelle Chang. Both also hold joint
appointments with Berkeley Lab and UC Berkeley. In addition, Chris Chang
is a Howard Hughes Medical Institute (HHMI) investigator. (See below
for a full list of the paper’s authors.)
The more carbon dioxide that is released into the atmosphere the
warmer the atmosphere becomes. Atmospheric carbon dioxide is now at its
highest level in at least three million years, primarily as a result of
the burning of fossil fuels. Yet fossil fuels, especially coal, will
remain a significant source of energy to meet human needs for the
foreseeable future. Technologies for sequestering carbon before it
escapes into the atmosphere are being pursued but all require the
captured carbon to be stored, a requirement that comes with its own
environmental challenges. 
(από αριστερά) Peidong Yang, Christopher Chang και Michelle Chang,
οι συντονιστές της ανάπτυξης ενός συστήματος τεχνητής φωτοσύνθεσης,
ικανού να μετατρέπει το διοξείδιο του άνθρακα σε χρήσιμα χημικά
προϊόντα, χρησιμοποιώντας μόνο νερό και ηλιακή ενέργεια – (Photo by Roy Kaltschmidt)
The artificial photosynthetic technique
developed by the Berkeley researchers solves the storage problem by
putting the captured carbon dioxide to good use.
“In natural photosynthesis, leaves
harvest solar energy and carbon dioxide is reduced and combined with
water for the synthesis of molecular products that form biomass,” says
Chris Chang, an expert in catalysts for carbon-neutral energy
conversions. “In our system, nanowires harvest solar energy and deliver
electrons to bacteria, where carbon dioxide is reduced and combined with
water for the synthesis of a variety of targeted, value-added chemical
products.”
By combining biocompatible
light-capturing nanowire arrays with select bacterial populations, the
new artificial photosynthesis system offers a win/win situation for the
environment: solar-powered green chemistry using sequestered carbon
dioxide.
“Our system represents an emerging
alliance between the fields of materials sciences and biology, where
opportunities to make new functional devices can mix and match
components of each discipline,” says Michelle Chang, an expert in
biosynthesis. “For example, the morphology of the nanowire array
protects the bacteria like Easter eggs buried in tall grass so that
these usually-oxygen sensitive organisms can survive in environmental
carbon-dioxide sources such as flue gases.”
The system starts with an “artificial
forest” of nanowire heterostructures, consisting of silicon and titanium
oxide nanowires, developed earlier by Yang and his research group.
“Our artificial forest is similar to the
chloroplasts in green plants,” Yang says. “When sunlight is absorbed,
photo-excited electron−hole pairs are generated in the silicon and
titanium oxide nanowires, which absorb different regions of the solar
spectrum. The photo-generated electrons in the silicon will be passed
onto bacteria for the CO2 reduction while the photo-generated holes in
the titanium oxide split water molecules to make oxygen.”
Απεικόνιση
εγκάρσιας τομής της συστοιχίας νανοσυρμάτων-βακτηρίων, η οποία
χρησιμοποιήθηκε στο επαναστατικό σύστημα τεχνητής φωτοσύνθεσης (credits ACS Publications)
Once the forest of nanowire arrays is
established, it is populated with microbial populations that produce
enzymes known to selectively catalyze the reduction of carbon dioxide.
For this study, the Berkeley team used Sporomusa ovata, an
anaerobic bacterium that readily accepts electrons directly from the
surrounding environment and uses them to reduce carbon dioxide.
“S. ovata is a great carbon
dioxide catalyst as it makes acetate, a versatile chemical intermediate
that can be used to manufacture a diverse array of useful chemicals,”
says Michelle Chang. “We were able to uniformly populate our nanowire
array with S. ovata using buffered brackish water with trace vitamins as the only organic component.”
Once the carbon dioxide has been reduced by S. ovata to acetate (or some other biosynthetic intermediate), genetically engineered E.coli are used to synthesize targeted chemical products. To improve the yields of targeted chemical products, the S. ovata and E.coli were
kept separate for this study. In the future, these two activities –
catalyzing and synthesizing – could be combined into a single step
process.
A key to the success of their artificial
photosynthesis system is the separation of the demanding requirements
for light-capture efficiency and catalytic activity that is made
possible by the nanowire/bacteria hybrid technology. With this approach,
the Berkeley team achieved a solar energy conversion efficiency of up
to 0.38-percent for about 200 hours under simulated sunlight, which is
about the same as that of a leaf.
The yields of target chemical molecules
produced from the acetate were also encouraging – as high as 26-percent
for butanol, a fuel comparable to gasoline, 25-percent for amorphadiene,
a precursor to the antimaleria drug artemisinin, and 52-percent for the
renewable and biodegradable plastic PHB. Improved performances are
anticipated with further refinements of the technology.
“We are currently working on our second
generation system which has a solar-to-chemical conversion efficiency of
three-percent,” Yang says. “Once we can reach a conversion efficiency
of 10-percent in a cost effective manner, the technology should
be commercially viable.”
In addition to the corresponding authors, other co-authors of the Nano Letters paper describing this research were Chong Liu, Joseph Gallagher, Kelsey Sakimoto and Eva Nichols.
You’re kindly requested to visit LBNL’s webpage, to meet the original press release, more information and related articles
Research paper
click to read via ACS Publications (recommended)
Nanowire–Bacteria Hybrids for Unassisted Solar Carbon Dioxide Fixation to Value-Added Chemicals
Chong Liu, Joseph J. Gallagher, Kelsey K. Sakimoto, Eva M. Nichols, Christopher J. Chang, Michelle C. Y. Chang, and Peidong Yang
Abstract
Direct solar-powered production of value-added chemicals from CO2 and H2O, a process that mimics natural photosynthesis, is of fundamental and practical interest. In natural photosynthesis, CO2 is first reduced to common biochemical building blocks using solar energy, which are subsequently used for the synthesis of the complex mixture of molecular products that form biomass. Here we report an artificial photosynthetic scheme that functions via a similar two-step process by developing a biocompatible light-capturing nanowire array that enables a direct interface with microbial systems. As a proof of principle, we demonstrate that a hybrid semiconductor nanowire–bacteria system can reduce CO2 at neutral pH to a wide array of chemical targets, such as fuels, polymers, and complex pharmaceutical precursors, using only solar energy input. The high-surface-area silicon nanowire array harvests light energy to provide reducing equivalents to the anaerobic bacterium, Sporomusa ovata, for the photoelectrochemical production of acetic acid under aerobic conditions (21% O2) with low overpotential (η < 200 mV), high Faradaic efficiency (up to 90%), and long-term stability (up to 200 h). The resulting acetate (∼6 g/L) can be activated to acetyl coenzyme A (acetyl-CoA) by genetically engineered Escherichia coli and used as a building block for a variety of value-added chemicals, such as n-butanol, polyhydroxybutyrate (PHB) polymer, and three different isoprenoid natural products. As such, interfacing biocompatible solid-state nanodevices with living systems provides a starting point for developing a programmable system of chemical synthesis entirely powered by sunlight.
Direct solar-powered production of value-added chemicals from CO2 and H2O, a process that mimics natural photosynthesis, is of fundamental and practical interest. In natural photosynthesis, CO2 is first reduced to common biochemical building blocks using solar energy, which are subsequently used for the synthesis of the complex mixture of molecular products that form biomass. Here we report an artificial photosynthetic scheme that functions via a similar two-step process by developing a biocompatible light-capturing nanowire array that enables a direct interface with microbial systems. As a proof of principle, we demonstrate that a hybrid semiconductor nanowire–bacteria system can reduce CO2 at neutral pH to a wide array of chemical targets, such as fuels, polymers, and complex pharmaceutical precursors, using only solar energy input. The high-surface-area silicon nanowire array harvests light energy to provide reducing equivalents to the anaerobic bacterium, Sporomusa ovata, for the photoelectrochemical production of acetic acid under aerobic conditions (21% O2) with low overpotential (η < 200 mV), high Faradaic efficiency (up to 90%), and long-term stability (up to 200 h). The resulting acetate (∼6 g/L) can be activated to acetyl coenzyme A (acetyl-CoA) by genetically engineered Escherichia coli and used as a building block for a variety of value-added chemicals, such as n-butanol, polyhydroxybutyrate (PHB) polymer, and three different isoprenoid natural products. As such, interfacing biocompatible solid-state nanodevices with living systems provides a starting point for developing a programmable system of chemical synthesis entirely powered by sunlight.
Source:
DOI: 10.1021/acs.nanolett.5b01254
Publication Date (Web): April 7, 2015
Copyright © 2015 American Chemical Society
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